A variety of integrated circuit packages are used for packaging semiconductor devices. Dual in-line packages (DIPs), pin grid arrays (PGAs), and surface mount packages have been widely used for many years. More recent package embodiments use flip-chip approaches and advanced interconnection substrates. Recessed chip multichip module (MCM) packages have been introduced in manufacture to reduce the package profile. In general, the state of the art package designs have relatively good EMI performance due largely to the short length of interconnections in BGA or solder bumped packages, and the compact interconnect strategy made possible by state of the art multichip modules. However, as operating frequencies continue to rise, even these package designs suffer from EMI problems. Operating frequencies in wireless applications are in the several to tens of gigabit range. Specialized computing devices also operate at these speeds. In these high frequency applications, even the relatively short leads of BGA and solder bumped packages are susceptible to stray electromagnetic radiation.
To combat EMI problems in IC packages, EMI shields are often incorporated in the package design. So-called Faraday cages in the form of wire grids have been built around the IC chip to shield the interconnections from stray fields. Metal cans are also provided to "encapsulate" IC chips and leads. These cans are usually fabricated using stamped metal (typically copper or aluminum). Consequently they add cost, size and weight to the IC package. In an effort to reduce the size and weight of the can, resort is made to perforating portions of the can. This reduces the bulk of the can but does not decrease the cost. Moreover, it reduces the effectiveness of the EMI shield.
As is known, EMI is disruptive to the proper operation of circuit components located near the source of the EMI. Accordingly, there is an identifiable need to reduce EMI susceptibility.